1. Field of the Invention
The present invention pertains to one-component polymer grouts.
2. Description of the Related Art
The process of grouting has been practiced now for millennia. The Romans, for example, employed a variety of grouts including pozzolanic grouts in building, road, and bath construction, as well as more conventional grouts based on calcined lime without pozzolan. One of the most widespread modern uses of grouting is to seal spaces between adjoining stones or tile, particularly the latter, for example in floors, walls, and particularly in shower enclosures. In the construction of such surfaces, the substrate, for example tile or stone, is adhered to a surface through the use of a tile adhesive, which is generally cementitious. In general, each tile or stone is separated from its neighbors by a relatively uniform distance, thus creating an empty space between the substrates. This empty space is filled with a “grout” of very high mineral content.
Cementitious grouts have been commonly used, and are relatively inexpensive. However, the application of cementitious grouts is labor-intensive and wasteful. For a tile floor or shower enclosure, for example, the dry grout composition is first mixed with water to form a relatively viscous semi-solid mixture, and this mixture is forced into the open spaces between the tiles using a tool. Tools for this use, for example, may be termed grouting floats or grouting paddles. In general, it is impossible to inject grout between tiles with devices such as caulking guns, since many if not most grouts are relatively dilatant, and thicken to a reversible, non-extrudable consistency upon application of pressure. By the use of a float, grout can easily be forced into the empty space between tiles and other substrates. However, a significant portion of grout also adheres to the face of the tiles or other substrate. In the case of porous substrates such as brick, the grout must be removed using strong acid. In the case of smooth substrates such as glazed tile, in general, the grout is allowed to partially cure, and then the grout which adheres to the face of the tile is removed with a wet sponge. The wet sponge is also used to smooth the grout to provide a uniform appearance. The craftsman must be careful that the grout does not harden so much that acid is again necessary to remove it. Moreover, the craftsman must also not use a sponge which is too wet, or use too much pressure on the sponge, as this action may actually remove grout from inbetween the substrates.
Cementitious grouts have the advantages of high compressive strength. However, the tensile strength of cementitious grouts is relatively low. The adhesion of cementitious grouts to the sides of the substrate and to the substrate support may vary over a wide range. To improve these qualities, it has been common to add very fine polymer particles to the grout. These polymer particles are preferably of the type referred to as “redispersible polymers” which are characterized by both a very small particle size, as well as film-forming capability. These polymers may be added in the dry state as a powder to the grout in a so-called “ready mix” formulation, or may be added in the form of an aqueous polymer dispersion, which is used in place of at least part and sometimes all of the mix water. The use of these polymers in “polymer-modified grout” can improve the adhesive qualities of the grout, the flexural strength of the grout, the tensile strength of the grout, and in some cases, with proper selection of polymer, the water resistance of the grout. Despite the advantages of polymer-modified grouts, which are somewhat more expensive than ordinary cementitious grouts, the grouting process is still essentially the same as that which has been used since at least Roman times, as discussed previously.
Curable “polymer grouts” have also been proposed. In these grouts, the hydraulically settable components of the cementitious grouts are replaced by curable polymers. For example, so-called “epoxy grouts” have been available for numerous years (e.g. U.S. Pat. No. 4,833,178). These grouts, however, suffer from several disadvantages: firstly, they must be supplied as a two-component mixture; secondly, once mixed, the mixture has little pot life and must be used rapidly, this mixing can lead to non-uniform color between mixes; and finally, the chemistry used may be hazardous to the health of the operator. Furthermore it is difficult to remove staining of the tiles which often results in a haze like layer on the surface of the tiles jointed together.
Grouts supplied as one-component systems have been proposed. But currently available one-component polymer grouts are typically water-based acrylics and are not intended, nor are they recommended, for use in high-traffic areas or areas with high exposure to water.
Therefore, it would be desirable to provide a grout for high-traffic applications which does not require mixing at the jobsite, which is a one-component rather than a two-component grout, and which provides color uniformity. It would be further desirable to provide a grout which offers high flexural modulus, good adhesion to substrates, water resistance similar to two-component epoxy grouts, and exceeds standard water-based acrylic one-component grouts. It would be further desirable to provide a one-component grout free of any hazardous ingredients.